Suicide and suicidal behavior are among the leading causes of adolescent mortality and morbidity. The majority of suicide decedents have their last clinical contact with primary care yet we lack empirically supported treatment strategies that can be deployed by primary care clinicians when youth present with acute suicide risk. In previous work, we developed a smartphone safety planning app, BRITE for psychiatrically hospitalized suicidal adolescents that supported an intervention that reduced suicidal events post-discharge by 42%. We now plan to adapt BRITE to use in primary care by providing step-by-step guidance to a primary care-based, non-mental health clinician on how to develop a safety plan for a suicidal adolescent and load this plan on the adolescent patient?s smartphone. This intervention, Guide2BRITE (G2B) aims to enhance the capability of primary care clinicians to effectively assess and manage acute suicide risk in adolescents via a guided 30 minute intervention to develop a safety plan with the adolescent and parent. During Phase 1, we will develop and pre-test components of the app-supported intervention including the virtual treatment manual, user interface, and presentation of step-by-step instructions and resulting safety plan with 5 primary care clinicians, adolescent patients and their parents to test the prototype, followed by an open pilot of 15 cases. For Phase 2, G2B will be further revised, and then tested using a randomized stepped wedge design in 6 pediatric primary care practices to pilot test the effectiveness of G2B among 100 adolescents aged 12.0-17.11 years who screen positive for acute suicide risk on the PHQ-9 item 9 (>2). G2B will provide the clinician with step-by-step instructions to populate the adolescents? app with a personally tailored safety plan, including the following components: (1) assessing lethality and restricting access to means; (2) identifying likely triggers of suicidal and self-harm urges and how to avoid and cope with them; (3) teaching skills via modeling and role-play to cope with suicidal and self-harm urges (emotion regulation, crisis survival skills, and utilizing existing social supports); and (4) identifying professional resources to access in a crisis should others means of coping fail. At the end of the intervention session, we will determine the immediate impact of G2B on adolescent distress and suicidal urges and clinician referrals to hospitals and emergency departments. Further, we will evaluate 6-, 12-, and 24-week outcomes from multiple perspectives: (1) the primary outcomes, trajectory of suicidal ideation, behavior, and non-suicidal self-injury; (2) provider, patient, and parent rating of usability and satisfaction; and (3) impact on firearms storage, impairment, visit cost, and use of emergency and hospital services. Since suicidal ideation is one of the strongest predictors of eventual suicidal behavior, the development of an easily disseminated, low-cost intervention that could be used by non-specialty mental health could have a large impact on the population burden of adolescent suicidal behavior. Moreover, G2B is innovative, as it is the first suicide prevention app geared to guide clinicians? interventions.